Method for producing a heating device having a heating profile for medical instruments and a heating device produced by that method

ABSTRACT

A method for producing a temperature control means ( 5   c   , 5   c ) of an elastic heating profile ( 1 ), which heat and/or cool a medical instrument inserted into a cavity ( 3 ) of the heating profile ( 1 ), are provided in bores ( 4   a   , 4   b   , 4   c , . . . ) having a bore diameter ( 110, 110′ ) which is smaller than the outer diameter ( 120, 120′ ) of the temperature control means ( 5   c   , 5   e ) to be inserted into the bores ( 4   a   , 4   b   , 4   c , . . . ). A positive and/or non-positive connection between the heating profile ( 1 ) and the received temperature control means ensures good thermal contact. The production costs for an operable heating profile or temperature control means are also reduced.

This application is a continuation of Ser. No. 11/822,891 filed Jul. 11,2007 and also claims Paris Convention priority of DE 10 2006 032 775.6filed Jul. 14, 2006 the complete disclosures of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

The invention relates to a method for producing an elastic heatingdevice having a heating profile designed to enclose and control thetemperature of medical instruments, comprising at least one cavity thatextends axially along the heating profile and can be accessed from theoutside, for inserting a medical instrument, and at least one axial borethat extends along the entire length of the heating profile, forreceiving a temperature control means.

Heating devices of this type are used to cool, heat and/or maintain adefined temperature of medical instruments, e.g. infusion tubes, andliquids or gases that flow through them.

A heating device of this type is disclosed e.g. in DE 827 702. A tubeused for injecting medical solutions is surrounded along its entirelength by channels in which a heating agent is circulated, wherein theheating agent channels are formed by one or more tubes. In order toenclose almost the entire periphery of the injection tube, several tubesare connected to each other through vulcanization, which can impair theheat transfer from the heating profile to the tube.

A further heating device, which is shown and described in DE 4 241 830A1, has a heating profile designed as a one-piece jacket which comprisesa continuous channel for receiving an infusion tube. The receivedinfusion tube is surrounded inside the channel by an electricallyheatable heat transfer body of metal. This can reduce the flexibility ofthe heating profile and its adjustability to the conditions at thelocation of use.

DE 4 444 180 C2 discloses a heating device using a heating profilehaving the shape of a slotted tube in which heating wires or heatingfluid channels are embedded. The heating profile is produced as asection of an endless profile into which the temperature control meansare inserted, embedded or vulcanized. Later introduction of thetemperature control means into a section of the endless profile requiresadditional production steps, such as insertion of heating wires. Goodthermal transfer from the temperature control means to the heatingprofile can thereby not be ensured. Direct insertion of the heatingwires, e.g. through vulcanization, increases the overall productionexpense, since e.g. the follow-up work for exposing the electricaltemperature control means requires significant time and work.

A further development of this heating profile which is disclosed in DE299 17 247 U1 has grooves for inserting and holding the infusion tube.This ensures good thermal transfer from the heating profile to aninserted infusion tube. Insertion of heating elements into bores of thegroove flanks, as disclosed in DE 4 444 180 C2, reduces the efficiencyof thermal transfer from the heating elements to the heating profile.

It is the underlying purpose of the invention to introduce a method forthe production of a heating device having a heating profile whichensures good thermal contact between the temperature control means andthe flexible heating profile, and which also permits provision of thetemperature control means independently of the heating profile beingproduced.

SUMMARY OF THE INVENTION

This object is achieved with a method for producing a heating devicewhich covers and controls a temperature of a medical instrument, themethod comprising the steps of:

-   -   a) preparing a heating profile from an elastic material, the        heating profile having at least one cavity which extends along        an axial extension thereof and which can be accessed from an        outside for insertion of the medical instrument, and with at        least one axial bore which extends along an entire length of the        heating profile, the at least one axial bore having an axial        bore diameter;    -   b) selecting a temperature control element, the temperature        control element having an outer surface with an outer surface        diameter that is larger than the axial bore diameter; and    -   c) pressing, following steps a) and b), the temperature control        element into the axial bore of the heating profile, thereby        widening the axial bore, wherein the widened axial bore presses        inwardly in a substantially radial direction against the outer        surface of the temperature control element, thereby establishing        good thermal contact between the temperature control element and        the heating profile.

The bore diameter in accordance with the invention is the inner diameterof the bore in the relaxed state, i.e. without inserted temperaturecontrol means. Due to the undersize of the bore compared to the maximumouter diameter of the temperature control means to be inserted into thebore, the bore must be widened or extended for inserting the temperaturecontrol means. After insertion of the temperature control means, theelastic material of the heating profile preferably surrounds the overallperipheral surface of the temperature control means. The naturalcompression of the widened bore produces a radial force that acts on theoverall periphery of the inserted temperature control means. Thetemperature control means is pressed into the flexible heating profilein a positive and/or non-positive fashion. This ensures good thermalcontact between the temperature control means and the heating profile.Another advantage results from the fact that the temperature controlmeans is securely held in the heating profile and cannot slip or fallout. The inventive heating profile is produced without temperaturecontrol means, typically as an extruded profile, into which thetemperature control means are subsequently pressed. With this productionmethod, the temperature control means can be machined independently ofthe heating profile and no time-consuming manual work or additional worksteps are required in order to provide an operational heating profile.The flexible heating profile is produced from plastic material orrubber, preferably silicon. The length of the heating profile istypically 100 to 200 cm, the diameter of the single-layered profile isapproximately 15 mm. A temperature control device or temperature controlsystem in accordance with the invention comprises the elastic heatingprofile and at least one temperature control means to be inserted intothe heating profile.

In a preferred embodiment of the inventive method, the heating profilehas several bores, in particular, of different bore diameters. The boresgenerally have a round cross-section but may also be elliptical or havean angular cross-section. The bores are preferably uniformly distributedaround the cavity enclosed by the heating profile. Different temperaturecontrol means, such as heating conductors and temperature sensors, maybe inserted into the bores. The inventive heating profile of thisembodiment may be divided into zones of different heating power.

In a further preferred embodiment of the invention, at least one, andpreferably two bores are provided in the heating profile, which extendalong or nearly along a neutral bending line (neutral fiber) of theheating profile when the heating profile is bent. The bore is suitablyprovided in the neutral fiber in order to avoid contraction or extensionin the longitudinal direction of a temperature control means introducedinto the bore when the heating profile is bent. It is almost impossibleto prevent bending of the heating profile during the intended use, e.g.guiding an infusion tube from a container containing the infusion to apatient. Introduction of sensitive temperature control means into a borewhose length does not vary when the heating profile is bent, preventsgreat strain and, in particular, damage due to excessive strain on thesensitive temperature control means.

The inventive heating profile is advantageously produced from a heatconducting material. The heating profile acts as a heat conductorbetween the temperature control means inserted into the bores and themedical instrument received in the cavity. The medical instrument, e.g.an infusion tube is heated and/or cooled by the temperature controlmeans. The temperature in or on the infusion tube can be determined bytemperature probes. The heating conductors and temperature sensors areadvantageously connected to a control and regulation unit.

In a preferred embodiment, the heating profile has a coating of aheat-insulating material on its outer surface, which is preferablyconnected to the material of the heating profile with material fit. Thecoating, which serves as an insulation layer, prevents thermal loss tothe outside or uncontrolled thermal influence from the outside to theinside to the medium to be heated in the medical instrument. In order tooptimize the insulation effect of the outer layer, the outer layer isundetachably connected to the heat-conducting and/or heat-storing innerregion of the heating profile. The two layers are directly connectedwith material fit to minimize formation of folds due to bending of theheating profile, which could impair the insulation effect of the outerlayer. The coating can be applied later e.g. by foaming. The heatingprofile is, however, advantageously produced from two layers of twodifferent materials in one work step by extruding the two layerstogether. This co-extrusion produces a direct, undetachable connectionbetween the insulating outer layer and the thermally conducting innerlayer of the heating profile, such that the insulation layer is almostundetachably connected to the heating profile and need not be fixedthereto later at great expense. Heating profiles of the most differenttypes can be coated with a heat-insulating material to constitute anindividual inventive concept independent of the inventive features ofthe independent claim. Elastic heating profiles which are foamed and/orcoated with material fit have the advantages of this embodiment evenwhen they do not have a bore.

An advantageous embodiment of the inventive method is characterized inthat the cavity is formed as a groove for receiving an infusion tube ora trocar. The infusion tube or the trocar can be inserted into thecavity via a slot or opening that extends along the axial direction ofthe heating profile. The cavity may, however, also be accessed via aslot which is cut for inserting or introducing the infusion tube ortrocar. The groove is designed like a counter-piece, i.e. its shape isadjusted to the medical instrument to be inserted, and advantageouslyundersized compared to the dimensions of the instrument. This generatesstress in the heating profile when the infusion tube is inserted,resulting in a force that acts radially on the infusion tube. Theinfusion tube is held in the heating profile in a positive and/ornon-positive fashion, thereby ensuring both good thermal contact betweenthe heating profile and the infusion tube and stationary mounting of theheating profile to the infusion tube. The groove is designed such thatthe heating profile surrounds or covers the received infusion tube onalmost its entire outer peripheral surface, and the insertion opening islargely closed again. The opening gap has a minimum size in order tolargely prevent heat from escaping through the gap during operation of aheating means with the inventive heating profile as well as uncontrolledheat input from the outside through this gap. An insulation layer isadvantageously provided on the outer surface right up to the boundary ofinsertion opening or insertion gap.

In addition, a temperature control means is provided in at least onebore. The temperature control means is/are advantageously designed as anelectric heating means, such as heating conductors or heating wiresand/or sensors, e.g. temperature probes. The heating wires are typicallydesigned as helices, and when they are introduced into and returned froma bore, as double helices. The temperature sensors or temperature probesare generally designed as NTC resistances. The inventive heating profilecan be finished and provided ready for use in dependence on theapplication by selecting corresponding heating or cooling means andcorresponding measuring means, e.g. for heating, cooling or insulation.The bores may also serve as fluid channels for heating or coolingagents. The heating means are thereby advantageously provided in boresalong the neutral bending lines. When a heating conductor is insertedinto a bore which is length-invariant during bending of the heatingprofile, i.e. along the neutral fiber, it is largely free from bendingloads, such as extension and compression.

Further advantages of the invention can be extracted from the figuresand the description of the drawing. The drawing shows embodiments of theinventive heating profile. The features shown in the figures are onlyschematic and are not to be taken to scale

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an embodiment of the inventive heating profile;

FIG. 2 shows a cross-section through a further embodiment of theinventive heating profile; and

FIG. 3 shows a longitudinal section through a short section of theinventive heating profile of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a perspective view of a section of a substantiallycylindrical heating profile 1. The heating profile 1 has an opening 2, acavity 3, and axial bores 4 a, 4 b, 4 c, 4 d, 4 e and 4 f along itsentire length. The cavity 3 is circularly surrounded by the heatingprofile 1 except for an interruption at the opening 2. The bores 4 a, 4b, . . . are embedded in the profile wall, and are oriented in the axialdirection 100 along the longitudinal extension of the heating profile 1,like the opening 2 and the cavity 3. The bores 4 a, 4 b, . . . aredisposed at almost regular intervals around the cavity 3, wherein thebores 4 a, 4 c, 4 d and 4 f have a bore diameter which corresponds to abore diameter 110 of the bore 4 c, is larger than the bore diameter ofthe bores 4 b and 4 e, and corresponds to a further bore diameter 120′of the bore 4 e. A first temperature control means 5 c and a secondtemperature control means 5 e are shown on each side of the heatingprofile 1. The outer surface 6 of the heating profile 1 has a wavycontour.

The first temperature control means 5 c is designed as a temperaturesensor having a first outer diameter 120. The second temperature controlmeans 5 e is a heating conductor with a second outer diameter 120′. Theheating profile 1 is shown as a blank, i.e. without inserted temperaturecontrol means 5 c and 5 e, and the bore diameters 110 and 110′ are shownin the relaxed state without compression. The bore diameter 110 of thebore 4 c is smaller than the first outer diameter 120 of the firsttemperature control means 5 c, such that the bore 4 c must be widened orextended for inserting the first temperature control means 5 c. Thefurther bore diameter 110′ of the bore 4 e and the second outer diameter120′ of the second temperature control means 5 e have a correspondingratio of dimensions.

The heating profile 1′ shown in cross-section in FIG. 2 differs fromthat of FIG. 1 in that a coating 8 is provided on the outer surface 6which defines an inner region 7 of the heating profile 1′. The coating 8which is disposed by foaming around the inner area 7 consists of aheat-insulating material. A medical instrument 9, in the present case aninfusion tube having a circular cross-section, is inserted into theheating profile 1′. The opening 2 is widened by an opening force in theopening direction 130 and 130′ in order to insert or press-in themedical instrument 9. The material stress in the heating profile 1′produces a restoring force in the closing direction 140 and 140′, whichlargely closes the opening 2 again after the insertion process. Thematerial and the shape of the heating profile 1′ are selected such thatthe medical instrument 9 is jacketed in a positive engagement fashion bythe inner area 7, and a radial force (e.g. indicated by arrow 160) actson the medical instrument 9. Due to this frictional connection, themedical instrument 9, the infusion tube, is safely held in the heatingprofile 1′, such that it cannot slip out of it.

Temperature control means 5 a, 5 c, 5 d, and 5 f designed as temperaturesensors and temperature control means 5 b and 5 e designed as heatingconductors are inserted into the heating profile 1′. The temperaturecontrol means 5 a, 5 c, 5 d and 5 f designed as temperature sensors eachhave a sensor head 50 indicated e.g. on the temperature control means 5d, which is directed towards the center of the heating profile 1′ andthe medical instrument 9 inserted at that location. The elastic,extendable heating profile 1′ abuts the temperature control means 5 a, 5b, . . . in a positive fashion and with compression force fit, therebyfixing them in the heating conductor 1′. The radial compression force isindicated on the first temperature control means 5 c e.g. by arrow 150.

FIG. 3 shows a longitudinal section through the heating profile 1′. Theheating profile 1′, which extends in the axial direction 100, is bent,thereby defining a compression area 10 and an extension area 11 in theheating profile 1′. The heating profile 1′ is compressed in thecompression area 10 due to pressure load (as indicated by arrow pair170). The heating profile 1′ is extended in the extension area due totensile load (as indicated by arrow pair 180). The length of a neutralbending line 12 that extends on the boundary line between thecompression area 10 and the extension area 11 does not change when theheating profile 1′ is bent. For this reason, the temperature controlmeans 5 b, which is disposed along the neutral bending line 12, ishardly compressed or stretched and thereby remains nearly free frombending loads.

The neutral fiber (neutral bending line 12), whose length does not varywhen the heating profile is bent, (neutral bending line 12) can be fixedby inserting a temperature control means (e.g. temperature control means5 b in FIG. 3) of a material which is considerably less elastic than thematerial of the heating profile. The solidity and flexibility of thetemperature control means is thereby selected such that, when theheating profile is bent or curved in dependence on the application, thetemperature control means follows the bending shape largely unchanged,while the surrounding material of the heating profile is extended orcompressed (compression area 10 and extension area 11). The heatingprofile is moreover not extended or compressed in an axial direction. Inother words, its length does not vary. All other bores, i.e. thoseoutside of the neutral fiber, have flexible feed lines. Fixing of aneutral fiber via a temperature control means, which is rigid comparedto the heating profile, can be realized with heating profiles of themost different types independently of a heating profile comprising thefeatures of claim 1, and represents a separate inventive concept. Theheating profile with defined bending behavior in accordance with theinvention has at least one bore for receiving a temperature controlmeans. It is also feasible to define several, preferably two neutralbending lines on the heating profile via corresponding temperaturecontrol means in the heating profile.

The temperature control means 5 c, 5 c of an elastic heating profile 1are provided in bores 4 a, 4 b, 4 c, . . . for heating and/or cooling amedical instrument which is inserted into a cavity 3 of the heatingprofile 1, the bores having a diameter 110, 110′ which is smaller thanthe outer diameter 120, 120′ of the temperature control means 5 c, 5 eto be introduced into the bores 4 a, 4 b, 4 c, . . . . A positive and/ornon-positive connection between the heating profile 1 and the receivedtemperature control means ensures good thermal contact. The productioncosts for an operable heating profile or temperature control means aremoreover reduced.

1. A method for producing a heating device which covers and controls atemperature of a medical instrument, the method comprising the steps of:a) preparing a heating profile from an elastic material, the heatingprofile having at least one cavity which extends along an axialextension thereof and which can be accessed from an outside forinsertion of the medical instrument and with at least one axial borewhich extends along an entire length of the heating profile, the atleast one axial bore having an axial bore diameter; b) selecting atemperature control element, the temperature control element having anouter surface with an outer surface diameter that is larger than theaxial bore diameter; and c) inserting, following steps a) and b), thetemperature control element into the axial bore of the heating profile,thereby widening the axial bore, wherein the widened axial bore pressesinwardly in a substantially radial direction against the outer surfaceof the temperature control element thereby establishing good thermalcontact between the temperature control element and the heating profile.2. The method of claim 1, wherein several bores are provided in theheating profile.
 3. The method of claim 2, wherein the bores havedifferent bore diameters.
 4. The method of claim 1, wherein at least onebore is provided in the heating profile which extends along orsubstantially along a neutral bending line of the heating profile whenthe heating profile is bent.
 5. The method of claim 4, wherein there aretwo bores.
 6. The method of claim 1, wherein the heating profile isproduced from a heat conducting material.
 7. The method of claim 1,wherein an outer surface of the heating profile is coated with aheat-insulating material coating.
 8. The method of claim 7, wherein theheat-insulating material coating is connected to the heating profilewith material fit.
 9. The method of claim 8, wherein the heating profileand the heat-insulating material coating are co-extruded in a singleextrusion process.
 10. The method of claim 1, wherein the cavity isdesigned as a groove for receiving an infusion tube or a trocar.
 11. Themethod of claim 1, wherein the temperature control means is disposed inat least one bore.
 12. The method of claim 11, wherein the temperaturecontrol means is designed as an electric heating means, a heatingconductor, a heating wire, a sensor, or a temperature probe.
 13. Themethod claim 12, wherein the temperature control means is disposed alonga neutral bending line.
 14. The heating device produced by the method ofclaim
 1. 15. The heating profile produced by the method of claim 1.